The present invention relates to a method and an apparatus for treating substrates in a fluid container with at least one fluid and with ultrasound, whereby oppositely disposed walls of the container are respectively provided with at least two ultrasound radiation areas that are or can be respectively individually activated.
Apparatus of this type are known, for example, from WO 95/02473, or from DE 197 22 423 belonging to the assignee of the present application. With these apparatus, the substrates are disposed in the fluid container during the treatment, and treatment fluids are introduced into the fluid container via an inlet opening.
At the same time, or subsequent to the fluid treatment, the substrates are irradiated with ultrasound in order to improve and accelerate the cleaning process. In this connection, it is important that the substrates be uniformly irradiated in order to generate a uniform cleaning effect. This uniform irradiation of the substrates is, however, not possible with the known apparatus because irradiation cones generate different irradiation intensities, or even dead angles occur. With the apparatus known from WO 95/02473, ultrasound radiation devices are provided on opposite side walls. The ultrasound radiation devices are formed by horizontally extending ultrasound strips. In order to achieve a uniform irradiation of the substrates, guide devices for the substrates are disposed on the inner surfaces of the side walls of the fluid container and the ultrasound radiation areas are offset. By doing so, only a limited improvement with regard to a uniform irradiation of the substrates is possible because these guide devices, which are arranged across from the ultrasound radiation areas, due to the thereby occurring dampening cause other irradiation intensities than is the case beyond the regions in which the guide devices are not present. Furthermore, this arrangement has the problem that upon irradiation of the substrates from the oppositely disposed side walls, reciprocal effects and wave quenching occur, especially with ultrasound waves that run into one another, as a result of which at best only a limited uniform irradiation of the substrates, and hence a uniform cleaning effect, are possible.
U.S. Pat. No. 4,909,266 discloses an apparatus for treating substrates with ultrasound where the ultrasound waves are selectively and briefly radiated in order to thereby increase a cleaning effect. This apparatus does not prevent any previously described reciprocal effects and wave quenching, which prevent a uniform cleaning effect.
JP 9-199 464 A (abstract) discloses an apparatus having groups of ultrasound radiation regions with different frequencies in order to remove particles having different sizes from a substrate that is to be cleaned. This apparatus also has the drawback that no uniform cleaning effect results because here again the ultrasound waves are in interaction or quenching.
The object of the invention is to provide a method and an apparatus for treating substrates that enable a more uniform and intensive treatment of the substrate surfaces with ultrasound.
This stated object is inventively realized in that the ultrasound radiation areas are respectively individually activated. The individual activation of the ultrasound radiation areas enables reciprocal effects, interferences and/or quenchings between or from ultrasound waves to occur that are irradiated from different and in particular oppositely disposed ultrasound radiation areas. This ensures a uniform, good and intensive treatment of the substrates with ultrasound over the entire substrate surfaces.
The ultrasound radiation areas of one container wall are preferably chronologically staggered, thereby reducing the aforementioned reciprocal effects. Pursuant to one preferred specific embodiment, each nth ultrasound radiation area, for example where n=3 then the first, fourth and seventh and/or the second, fifth and eighth, etc., is simultaneously activated, as a consequence of which a plurality, i.e. a group, of radiation areas is activated, so that in contrast to a respective individual chronologically staggered activation, the treatment speed can be increased without, however, having the aforementioned disadvantageous reciprocal effects occur.
Pursuant to a particularly advantageous specific embodiment of the invention, the ultrasound radiation areas of one container wall are activated in a chronological relationship to the ultrasound radiation areas of the other container wall, whereby advantageously ultrasound radiation areas of the container walls disposed across from one another are not activated simultaneously. As a consequence of this activation, in a particularly advantageous manner the irradiation of opposite container walls can be carried out without the disadvantageous reciprocal effects, interferences, attenuation or quenchings occurring between the ultrasound waves radiated from the oppositely disposed container walls.
During the treatment process the substrates are advantageously moved relative to the ultrasound radiation areas, in particular being raised and lowered, in order to enable a uniform treatment of the substrates over the surfaces thereof.
Pursuant to one particularly advantageous specific embodiment of the invention, the individual ultrasound radiation areas of one container wall are spatially offset relative to the ultrasound radiation areas of the other container wall in order to prevent regions where no ultrasound treatment occurs, since the radiation areas of the oppositely disposed container walls overlap one another.
The ultrasound radiation areas are advantageously strip-shaped, and are disposed either vertically or horizontally.